Chromosomes and Inheritance Chapter 12 ( )

Parts of Chromosomes Telomeres Centromeres Locus p arm q arm Telomeres

Karyotype Picture of chromosomes Homologous chromosomes contain the same genes Often arranged with autosomes (found in both sexes) in descending order and sex chromosomes separate

X-Linked Inheritance Color blindness (X-linked recessive) Hemophilia (X-linked recessive)

Autosomal Recessive Disorders Sickle-Cell Anemia Red blood cells take on a curved shape Clot in the capillaries Decreased oxygen supply to brain & muscles Werner Syndrome Premature aging Begins during adolescence Mapped to chromosome 8

Autosomal Dominant Disorders Polydactyly Extra fingers or toes Achondroplasia Growth related defect Cartilage growth in the long bones is slow Results in short stature

Retinitis Pigmentosa X-linked recessive, Autosomal dominant or Autosomal recessive Eye diseases that affect the retina Degeneration of cones and rods in the eye Loss peripheral vision

Pedigree Analysis Diagrams of family history Used to determine if a disease or condition is dominant, recessive, or X-linked Use symbols to represent individuals

Polyploidy The addition of one or more sets of chromosomes to a genome Malfunction in meiosis Egg or sperm end up with two sets of chromosomes Detrimental in humans Preferred in some plant species

Aneuploidy One chromosome too many or missing one chromosome Common in humans Common in miscarriages Ex. Down syndrome Result of nondisjunction

Nondisjunction

Most result in a miscarriage, except for those that occur on chromosome 13, 18, or 21

Trisomy Zygote ends up with 3 chromosomes instead of 2 for a given pair of chromosome.

Down Syndrome (Trisomy 21) 1 in 800-1,000 births Large tongue Flat face Single crease across palm Slanted eyes Mental retardation -Some are not Increased risk for congenital hear defects and leukemia

Edward Syndrome (Trisomy 18) 1 in 3,000 births Affects more girls than boys Heart defects Displaced liver Clenched hands Low-set ears Severe retardation 98% abort Lifespan < 1 year

Patau Syndrome (Trisomy 13) 1 in 10,000 births Cleft lip and palate Small eyes Extra fingers & toes –polydactylism Defects –Heart –Brain –Kidney Most abort Live span < 1 month

Klinefelter Syndrome 1 in 500-1,000 births Breast development Small testes Sterile Autoimmune disorders Low intelligence –Not retarded

Turner Syndrome 1 in 2,500 births Short Not go through puberty Webbed neck Dropping eyelids Produce little estrogen Sterile Increased risk for obesity, cataracts, arthritis, scoliosis

Aberrations within chromosomes Deletions: Ex. Cri-du-chat syndrome Inversions: Ex. Acute Myeloid Leukemia Translocations: Duplications:

Deletion Part of a chromosome is deleted

Cat Cry Syndrome Deletion on chromosome 5 Prader-Willi Syndrome Deletion on chromosome 15

Inversion Part of a chromosome is inverted A B C D E F G H I J A B C D E F J I H G

Inversion of Chromosome 16 Inversion between chromosome 13 and 22 Acute myeloid leukemia

Translocation Part of a chromosome attaches to a nonhomologous chromosome

Translocation of Between Chromosomes 1 and 3 Part of chromosome 3 attached to chromosome 1 Acute myeloid leukemia

Duplication Part of a chromosome is duplicated

Chromosome 10q duplication syndrome Mental retardation Defects in many organs –Heart –Kidneys –Bones –Muscles Life span less than 1 year